THE FLIGHT OF BIRDS. 25 



The Flight of Birds. 



The next thing to consider is the power and facility by which 

 birds carry out their instinctive desire of migration. 



It is one of the distinctions between man and many of the 

 lower animals that they can fly, while he cannot. Our inferiors 

 in other respects, it must be confessed that in the question of 

 wings they, not we, are " on the side of the angels." 



Man envies the bird for its marvellous powers of flight, and 

 has repeatedly tried to supply the want by artificial means; but 

 as yet without success — unless through the wingless flight of 

 the balloon. But, with the knowledge now possessed of the 

 laws which govern natural flight, with the increasing command 

 of natural forces, and the greater mechanical skill of man, it is 

 not impossible that artificial flight may yet be accomplished. 



It is supposed by many that it is the lightness of birds — by 

 air cells and hollow bones — that renders their flight possible ; but 

 insects, bats, and birds are as heavy, bulk for bulk, as most other 

 creatures, and flight can be performed perfectly by animals which 

 have neither air-sacs nor hollow bones. 



Strange though it may appear, it is the weight — not the 

 buoyancy — of birds which enables them to fly. Were they 

 lighter than air flight would be impossible. They could merely 

 float in the aerial ocean like a balloon, and, like it, would be liable 

 to be blown hither and thither by every breath of wind. Birds 

 are immensely heavier than the air they navigate, and it is this 

 weight that gives the momentum, which, when properly 

 directed, becomes transformed into sustaining and propelling 

 power. The momentum which weight adds to a bird in full 

 flight is strikingly illustrated in the effect produced when a bird 

 strikes a lighthouse. A wild-duck has been known to smash 

 one of the glasses of Eddystone lighthouse, with the result not 

 only of its own instant destruction, but of the complete smashing 

 of the glass, fully an inch thick. It is well known that this 

 momentum has been utilised in the catching of such birds as the 

 Solan goose, by fixing herring on boards, down upon which the 

 bird comes with such force as to break its neck. They have 

 been known to plunge half through the bottom of a boat 

 engaged at the herring fishing. 



The extent of wing does not bear any fixed relation to the 

 weight of the bird, there being many heavy-bodied birds with 

 small wings, and as many light birds with large wings. A 

 c 



